Double Seismic Zone for Deep Earthquakes in the Izu-Bonin Subduction Zone

Abstract
A double seismic zone for deep earthquakes was found in the Izu-Bonin region. An analysis of SP -converted phases confirms that the deep seismic zone consists of two layers separated by ∼20 kilometers. Numerical modeling of the thermal structure implies that the hypocenters are located along isotherms of 500° to 550°C, which is consistent with the hypothesis that deep earthquakes result from the phase transition of metastable olivine to a high-pressure phase in the subducting slab.